So last night my husband asked me why tuna has mercury in it. I thought, “oh, I know this. They eat stuff with it.” Then, by complete coincidence I saw this article today. The article is about why salt water fish have more mercury in them than fresh water fish. It says that sunlight naturally breaks down the most toxic forms of mercury, but in salt water, the mercury is tougher to break down because it bonds to stuff. Now, the problem, of course, is that fish live in this water, and that they store the mercury in their organs. So just be sure to know how much of this stuff you could be ingesting.